Tal Afar, about 80 km (50 miles) west of Mosul, experienced cycles of sectarian violence between Sunnis and Shi’ites after the U.S.-led invasion of Iraq in 2003, and produced some of Islamic State’s most senior commanders.

The city, which had about 200,000 residents, came under the militants’ control when Islamic State overran swathes of Iraq’s north in 2014.

It fell to Iraqi Security Forces, backed by the U.S.-led coalition, in August 2017, the last area to be retaken in the north before fighting moved to the Syrian border.

A heavy security presence has remained since then and the city has been mostly quiet.